1. Field of the Invention
The invention relates to a technique for, when a current value or voltage value of an electrical storage device is detected, utilizing the detected current value or the detected voltage value in consideration of a detection error due to ripple current.
2. Description of Related Art
Japanese Patent Application Publication No. 2011-117796 (JP 2011-117796 A) describes that the detection timing of a voltage value and the detection timing of a current value need to be synchronized with each other in order to accurately evaluate the internal resistance of a battery. Here, when there is ripple current, the correspondence relationship between a current value and a voltage value deviates due to a deviation between the detection timing of a voltage value and the detection timing of a current value.
Therefore, when there is ripple current, it is possible to prevent erroneous determination that there is an abnormality in the internal resistance if the internal resistance is not calculated on the basis of the detected voltage value and the detected current value. That is, when there is ripple current, it is possible not to use the detected voltage value and the detected current value at the time of calculating the internal resistance.
Here, as is described in JP 2011-117796 A, the peak-to-peak value of ripple current varies on the basis of the rotation speed of a motor, so it is possible to acquire an increase in ripple current by monitoring the rotation speed of the motor.
In a system that includes a motor and a step-up circuit, ripple current increases through not only the rotation speed (number of revolutions) of the motor but also the switching operation of the step-up circuit. Here, for example, if the internal resistance is calculated or not calculated on the basis of only the rotation speed of the motor, an opportunity to calculate the internal resistance may be limited more than necessary.